Electrical space discharge tube



Aug. 27, 1946. R. wcm- 2,406,422

ELECTRICAL SPACE DTSCHARGEl TUBE Filed Jan. 27, 1945 '2 sheets-sheet 1/oss Waan,

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ELECTRICAL SPACE DISCHARGETUBE v Filed Jan. 2'?, 1945 la f 2 Sheds-Sheet2 ffasWoog/j Patented Aug. 27, 1946 ELECTRICAL SPACE DISCHARGE TUBE RossWood, Waltham, Mass., assignor to Ray theon Manufacturing Company,Newton, Mass., a corporation of Delaware Application January 27, 1945,serial No. 524,866 c claims. (Grasa-27.5)

This invention relates to electrical space discharge tubes of smalldimensions, such as those used in small portable devices, pocket radiosand hearing aids, for example, which may be carried on the person. Inorder that the tubes may be utilized in such' devices theyn must ofnecessity be made extremely small.

One of the objects of the present invention is to provide a tube of thegeneral type referred to in which certain tube elements and theirarrangement are such that said elements can be assembled ina very smallspace, thus materially reducing the size of the tube.

Another object of the invention is to provide a tube f the type referredto which' combines small size with relatively high amplification and lowoperating voltage.

Another object of the present invention is to` provide a tube comprisinga single filament cathode supported at two points only, a plurality ofanodes cooperating with said cathode and a plurality of additionalelectrodes between said cathode and each anode.

A further object of the invention is to provide a double space chargetetrode in which the two tetrodes have a common cathode and are adaptedto operate in cascade.

These and such other aims and objects of the invention as mayhereinafter appear will be best understood from the followingdescription, taken in connection with the accompanying drawings, of atube incorporating one embodiment of the invention herein presented forillustrative purposes.

In the drawings:

Fig. 1 is a longitudinal section of a tube incorporating oneillustrative embodiment of the in vention; v

Fig. 2 is a longitudinal cross-section on line 2--2 of Fig. 3;

Fig. 3 is a cross-section on line 3-3 of Fig. 1; and

Fig. 4 is a section on line 4-4 of Fig. 2.

'I'h'e illustrative embodiment of the invention shown in the drawingscomprises an evacuated .V

envelope 2 of glass or other suitable material containing the tubeassembly which comprises a single lament cathode 4, a pair of anodeplates 6 and 8 and a plurality of grids, herein three, I0, I2 and I 4,said grid Il) surrounding said cathode and said grids I2 and I4 beinginterposed between said grid ID and said anode plates 6 and 8respectively. Said filamentary cathode, anode plates and grids aresuitably spaced by upper and lower insulating spacing members I6 and I8of mica or other suitable insulating material provided with suitablyspaced holes through which said lamentary cathode and the supportingmeans for said anode plates and said grids extend, as will hereinaftermore fully appear. At their edges said spacing members are provided withresilient projections 28 (see Fig. 3) for resiliently engaging the wallof said envelope.

The two anode plates 6 and 8 are each mounted in a frame 22 of nickelwire or other suitable material consisting of a straight top portion 24and depending arms 26 and 28 (see Fig. l).

To assemble the anode structure, the arms 26 and 28 ofthe anode framesare inserted through holes in said upper spacing member I6 and saidframes are then pressed down until said straight portion 24 of each ofsaid frames rests upon the upper surface of said spacing member I6,whereupon the said anode plates 6 and 8 are welded at their edges tosaid arms 26 and 28 of their frames, l with the upper edge of each anodeplate against the under surface of said spacing member I6. Said anodeplates may be provided with marginal grooves along their side edges toreceive and the better to locate saidside arms 26 and 28. Said arms ofboth anode plates are then inserted through holes in the lowerspacingmember I8. A lead-in conductor 30 is welded to the anodesupporting arm 26 of anode plate 6 and another lead-in conductor 32 iswelded to the anode supporting arm 28 of anode plate 8 diagonally acrossfrom said anode supporting arm 26, both of said welds being close upagainst the underside of said spacing member I8 to hold said spacingmember in place on said arms. The anode assembly is thus completed andthe two anode plates are electrically connected to their lead-in wiresand securely fastened in place in the insulating spacing members I6 andI8.

The grid I0 is wound upon and supported by the grid rods 36 and 38, andsurrounds the filamentary cathode 4. Grids I2 and I4 are control grids,the former being supported by rods 40 and 42 and the latter by rods 44and 46.

The grid supporting rods are all in a straight line and the rods towhich the ends of the grid members of one of the control grids aresecured, alternate withI the rods to which the ends of the grid membersof the other control grid are secured. Actually the ends of the gridmembers of each of the control grids are secured at one end to anendmost grid supporting rod, and at th'e other end to the next to theendmost grid supporting rod, so that the two control grids actuallyoverlap longitudinally of their grid members. This arrangement of th'etwo control grids, therefore, provides a very compact grid structure andcorrespondingly reduces the size of the tube.

At its upper end the lamentary cathode 4 is welded to one end of aconducting spring member 48 which is welded at its other end to a rodlextending through said spacing rmembers I6 and I8. The lower end of saidfilamentary cathode is welded to a tab 50 which is welded to a crossbar52 carried by two studs 54 riveted to the lspacing. .member I and towhichr cross-.bar52 is welded in turn'alead-in conductor 56, Thelamentary cathode 4 passes through a triangular slot 58 in said spacingmember I8 and throughY `a similar slot (not shown) in the spacing memberi5 and'is maintained in an apex of each Vof Vsaid slots by the resilienttension exerted upon said lamentary cathode by the aforesaid springmem--v `ber 48.

In addition to the above-mentioned lead-in 1conductors 30 and 32 for the"two anode plates, and the lead-in conductor 56 for the lamentarycathode, additional lead-in conductors 62, 64, 66 and 68 are providedfor the lamentary cathgrid I2 supporting rod 4e.

All of the above lead-in conductors are sealed `through a suitable pressformed externally lupon the base 0f the envelope 2.

A getter 'I2 may be conveniently welded to the upper end of thesupporting rod 46 of the half The arrangement of the electrodes andother elements of the tube embodying the present invention is extremelycompact with the result that `the tube 4may be very small, and theelectrode assemblyzcomprising a single cathodecooperatjing with twoanodes and three grids constitutes in fact a double space charge tetrodein which the two tetrodes are sufliciently isolated for operating incascade. rihe present invention there- `fore provides 'a tube whichproduces a degree of amplification substantially equal to that `ob`tainable from two Separate complete tetrodes, while dispensing with theadditional structure and consequent greater bulk which the addition ofthe second cathode would involve.

While in the illustrative embodiment ofthe invention herein describedtwo control grids and twoanode plates are used, it will be apparent tothose vskilledV in the art that 'a tube comprising a greater number ofcontrol grids and vanodes lwould fall within the scope of vthe presentinvention, and this would be true also oi the combination of a singlefilament cathode with a plurality of cooperating anodes and apluralityof additional electrodes between-the common cathode and eachanode, the number of additional electrodes between the common cathodeand one of said anodes not necessarily` being the same as the numberof-additional electrodes between said common cathode and another of saidanodes. Thus a tube having a'certain number of electrodes could becombined with'another tube having a lesser ora greater number ofelectrodes, the two tubes having a single filament cathode in common,and still be within the scope of the present invention. f Y Y The drainin small batteries that must be used in portable devices, to be carriedon the person, such as those to which this invention mainly relates, isa serious matter. V'Ihe present invention aims to reduce this loss ofenergy as much as possible. It has' been demonstrated that anappreciable part of the energy-delivered tothe cathode is lost due tothe escape of heat from the Epoints o f ,Contact of thecathode with thesupporting structure.

In accordance with the present invention, therefore, a single iilamentcath- Y ode is used which having only two ends or points of contact withthe supporting structure reduces to a minimum theloss of energy from theabovementionedcause 1 I am aware'that the present invention can beembodied in other specific forms without departing from the spirit oressential attributes thereof, yand I'therefore desire to presentdescription to I be considered in all respects as illustrative and theother end to an intermediate rod.

not restrictive, reference being had to the appended claims rather thanto the aforesaid deoperating anode at each side o'f said cathode, a

space charge grid surrounding saidrcathode, and two substantiallyparallel control grids, one between each of said anodes and said spacecharge grid, said control grids overlapping each other lengthwise oftheir grid members.

k3. In an electrical space discharge tube, the Acombination of lacathode, a cooperating anode ateach side of sa'id'cathode, a spacecharge grid surrounding's'a'id cathode, a vcontrol grid between saidspace charge grid and each-anode, said control grids being substantiallyparallel', and rods disposed inva straight line 'for supporting- -saidgrids, the grid members of each f said-control grids beingsecured at one'end to an Ae'ndmost rod of said line of grid supporting rodsandjat e.'In an electrical space discharge "tube, the combination of afsinglefilament cathode, Vla cooperating anode at each side of said cathode, a

`space charge grid surrounding sa'idcathode, a

` control grid between said spaceV charge grid and each anode, and rodsdisposed in astraiglit line for supporting said grids, the giidmembersof eachofrs'aid control grids being secured atone l endlto an endmostrodof said line of gridY :sup-

ginal portions of the otherf porting rods and at the other end to therodVnext to the en'dmost rod.

5. In an electrical space discharge tube, a

cathode, two anodes, one on each side 'of said cathode, a space chargegrid surrounding said cathodaand two control grids, one between each ofsaid anodes and said space charge grid, said control grids beingparallel and offset with-'reyspect to each other.

of said anodes and said space charge grid-said Y vcontrol grids .havingoffset central portions and Vcurved marginal portions, Vwith the curvedmarginal portions of one overlapping the curve-d `inar-

